creating a volume rest state

[dannyODF]

say I was creating a volume without a simulation, or I was pulling in density primatives from various simulations and mixing them together. Is it possible to create a new rest state? How does the shader know what volume is for density, and what volume is for rest? Where is that defined and how can I access that information? Whenever I create a new volume it seems to be treated as density,

thanks,

[anim]

you can give name to each volume primitive

either at creation in Volume SOP or IsoOffset SOP

or any time after by Name SOP

each volume primitive is a float value

but if you have 3 primitives named name.x, name.y, name.z Houdini will use them as single vector volume (like vel, just middle click on volume produced by pyro, there is all kinds of primitives named density, vel.x, vel.y, vel.z, rest.x, rest.y, rest.z, ...)

you can access those primitives in Volume VOP simply by Parameter VOP with the same name like float parameter density will contain values of density for each voxel, or vector parameter rest will contain rest position (according to rest.x, rest.y, rest.z volume primitives) you can even use Parameter VOP to export values to volume primitives (if primitives with such names already exist)

[SpencerL]

you can give name to each volume primitive

either at creation in Volume SOP or IsoOffset SOP

or any time after by Name SOP

each volume primitive is a float value

but if you have 3 primitives named name.x, name.y, name.z Houdini will use them as single vector volume (like vel, just middle click on volume produced by pyro, there is all kinds of primitives named density, vel.x, vel.y, vel.z, rest.x, rest.y, rest.z, ...)

you can access those primitives in Volume VOP simply by Parameter VOP with the same name like float parameter density will contain values of density for each voxel, or vector parameter rest will contain rest position (according to rest.x, rest.y, rest.z volume primitives) you can even use Parameter VOP to export values to volume primitives (if primitives with such names already exist)

to add to Anim's comments, the default pyro shader accepts dual rest fields called "rest" and "rest2", this is to basically reset your rest field every "n" frames which you can set in the pyro solver. The second rest field is offset by "n" frames from the first and then it blends between the two over time. This helps keep whatever you are mapping from stretching.